Mr Brown urged both sides, who will meet at the Advisory, Conciliation and Arbitration Service (ACAS), to settle their dispute. The union is claiming a 13.2 per cent pay rise.

If a deal is not reached then 641 drivers will stage a four-day strike from Friday, starving Shell's 892 petrol stations of supplies.

Mr Brown's spokesman said that contingency plans were in place.

"We believe that this strike is unnecessary and we would want to ensure that nothing was done that inconvenienced the public," he said.

"But the most responsible thing the public can do is to continue to buy as normal."

The Government has already started taking emergency measures, suspending competition legislation to allow oil companies to talk to each other over stock levels.

With Shell accounting for around 10 per cent of forecourts in the country, this would allow other petrol and diesel retailers to ship in extra supplies to their garages to make sure that local areas do not run short.

Special steps would also have to be taken to ensure that motorway service areas supplied by Shell – Fleet on the M3 and Taunton Deane on the M5 – had stocks at all times.

If the crisis worsens, more drastic measures could be taken, using powers under the 1976 Energy Act.

These would rationing and include reserving around 600 filling stations for the emergency services and other key users.

Petrol retailers pleaded with motorists to stick to their normal pattern of fuel buying, rather than stampeding to petrol stations.

A similar message came from the AA. "We just don't want a repetition of the mayhem that happened in Scotland after Grangemouth," a spokesman said.

"We don't believe there will be a need to panic buy. In urban areas, where there are alternatives, there will be no problems.

"The situation may be different in some rural areas where Shell is the only supplier, but we understand that contingency plans have been drawn up by the Government and petrol companies."